Research is proposed to use the engineering principles of fluid mechanics and mass transfer to investigate those aspects of olfactory function and dysfunction, in the rat and human nasal cavity, that depend on nasal cavity anatomy, odorant solubility, chemical reaction, air flow, and diffusion. We will construct a 50x enlarged scale model of the rat nasal cavity and establish fluid mechanical similarity between this large model and the real rat nasal cavity by matching the dimensionless Reynolds and Strouhal numbers between the two. We will make velocity measurements inside this model under conditions simulating the rat sniff experiments being conducted in project #2. We will also continue to make velocity profile measurements in our large scale human nasal cavity model as we introduce anatomic variations in it characteristic of various clinical condiitons of olfactory dysfunction suggested by the results obtained in project #1 and in the various other projects. Simultaneously with these measurements in the large scale physical models, we will continue to develop 3-D finite element numerical models of the mass transport aspects of olfaction in the rat and human. The numerical models will be validated by comparing their predictions tot he experimental measurements obtained in the physical models. The numerical models will allow us to investigate all conductive aspects of olfactory dysfunction relatively quickly by changing nasal cavity geometry, mucus depth and chemical composition, and odorant concentration boundary condition at the air-mucus interface. Together, the physical and numerical nasal cavity models constitute a powerful new approach to investigating dysfunction which will interface closely with the other projects in the proposal.